Previous studies in our laboratory have established the existence of cardiopulmonary reflexes with receptors located within various chambers of the heart, major extrapulmonary intrathoracic blood vessels, and in the pulmonary circulation. Some of the reflexes can be initiated through physiological or electrical activation of mechanoreceptors with vagal afferents, and some of the reflexes can be initiated through receptors with spinal or sympathetic afferent pathways. The reflexes may be either predominantly depressor (bradycardia and hypotension) such as vagal reflexes of left ventricular origin or, in some instances, pressor (tachycardia and hypertension) such as some of the spinal reflexes of cardiac origin. Both cardiac vagal and cardiac sympathetic afferents may be capable of initiating changes in respiratory frequency and depth. The predominant effect on breathing appears to be inhibitory. We propose to study the interaction of cardiopulmonary reflexes and sino-aortic baroreceptors in circulatory control and to establish the neuroanatomic bases for the cardiopulmonary reflexes utilizing autoradiographic techniques, Wallerian degeneration induced by selective denervation, and evoked potential measurements. In addition, we will study the role of altered reflex regulation in circulatory control induced by chronic animal models for coarctation of the aorta, aortic and pulmonic stenosis, and chronic heart failure.